@article{10_4153_CJM_1972_021_0,
     author = {Ault, Janet E.},
     title = {Extensions of {One} {Primitive} {Inverse} {Semigroup} by {Another}},
     journal = {Canadian journal of mathematics},
     pages = {270--278},
     year = {1972},
     volume = {24},
     number = {2},
     doi = {10.4153/CJM-1972-021-0},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-1972-021-0/}
}